# Estimating Distance from Parallaxes (gdr2_contrib.starhorse)

## Description

Estimating Distance from Parallaxes. IV. Distances to 1.33 Billion Stars in Gaia Data Release 2. For the vast majority of stars in the second Gaia data release, reliable distances cannot be obtained by inverting the parallax. A correct inference procedure must instead be used to account for the nonlinearity of the transformation and the asymmetry of the resulting probability distribution. Here, we infer distances to essentially all 1.33 billion stars with parallaxes published in the second Gaia data release. This is done using a weak distance prior that varies smoothly as a function of Galactic longitude and latitude according to a Galaxy model. The irreducible uncertainty in the distance estimate is characterized by the lower and upper bounds of an asymmetric confidence interval. Although more precise distances can be estimated for a subset of the stars using additional data (such as photometry), our goal is to provide purely geometric distance estimates, independent of assumptions about the physical properties of, or interstellar extinction toward, individual stars. We analyze the characteristics of the catalog and validate it using clusters.

## Columns

Name | Type | UCD | Unit | Description |
---|---|---|---|---|

source_id | long | meta.id | Unique source identifier (unique within a particular Data Release) | |

sh_photoflag | char | StarHorse photometry input flag | ||

sh_parallaxflag | char | StarHorse parallax input flag | ||

sh_gaiaflag | char | StarHorse GDR2 quality flag | ||

sh_outflag | char | StarHorse output quality flag | ||

dist05 | double | pos.distance | StarHorse distance, 5th percentile | |

dist16 | double | pos.distance | StarHorse distance, 16th percentile | |

dist50 | double | pos.distance | StarHorse distance, 50th percentile | |

dist84 | double | pos.distance | StarHorse distance, 84th percentile | |

dist95 | double | pos.distance | StarHorse distance, 95th percentile | |

av05 | double | phys.absorption.gal | Magnitude[mag] | StarHorse line-of-sight extinction at 5420 nm, A_V, 5th percentile |

av16 | double | phys.absorption.gal | Magnitude[mag] | StarHorse line-of-sight extinction at 5420 nm, A_V, 16th percentile |

av50 | double | phys.absorption.gal | Magnitude[mag] | StarHorse line-of-sight extinction at 5420 nm, A_V, 50th percentile |

av84 | double | phys.absorption.gal | Magnitude[mag] | StarHorse line-of-sight extinction at 5420 nm, A_V, 84th percentile |

av95 | double | phys.absorption.gal | Magnitude[mag] | StarHorse line-of-sight extinction at 5420 nm, A_V, 95th percentile |

ag50 | double | phys.absorption.gal | Magnitude[mag] | StarHorse line-of-sight extinction in the Gaia DR2 G band (Maiz-Apellaniz & Weiler 2018), A_G, 50th percentile |

teff16 | double | phys.temperature.effective | Temperature[K] | StarHorse effective temperature, 16th percentile |

teff50 | double | phys.temperature.effective | Temperature[K] | StarHorse effective temperature, 50th percentile |

teff84 | double | phys.temperature.effective | Temperature[K] | StarHorse effective temperature, 84th percentile |

logg16 | double | phys.gravity | cgs[dex] | StarHorse surface gravity, 16th percentile |

logg50 | double | phys.gravity | StarHorse surface gravity, 50th percentile | |

logg84 | double | phys.gravity | cgs[dex] | StarHorse surface gravity, 84th percentile |

met16 | double | phys.abund.Z | cgs[dex] | StarHorse metallicity, 16th percentile |

met50 | double | phys.abund.Z | cgs[dex] | StarHorse metallicity, 50th percentile |

met84 | double | phys.abund.Z | cgs[dex] | StarHorse metallicity, 84th percentile |

mass16 | double | phys.mass | Mass[solar] | StarHorse stellar mass, 16th percentile |

mass50 | double | phys.mass | Mass[solar] | StarHorse stellar mass, 50th percentile |

mass84 | double | phys.mass | Mass[solar] | StarHorse stellar mass, 84th percentile |

abp50 | double | phys.absorption.gal | Magnitude[mag] | StarHorse line-of-sight extinction in the G_BP band (Maiz-Apellaniz & Weiler 2018), A_BP, 50th percentile |

arp50 | double | phys.absorption.gal | Magnitude[mag] | StarHorse line-of-sight extinction in the G_RP band (Maiz-Apellaniz & Weiler 2018), A_RP, 50th percentile |

bprp0 | double | Magnitude[mag] | StarHorse dereddened G_BP - G_RP colour, derived from phot_bp_mean_mag, phot_rp_mean_mag, Teff50 and AV50 | |

mg0 | double | Magnitude[mag] | StarHorse absolute magnitude, derived from phot_g_mean_mag_oct2018, dist50, and AG50 | |

xgal | double | pos.distance | kpc | StarHorse Galactocentric Cartesian X coordinate, derived from dist50 |

ygal | double | pos.distance | kpc | StarHorse Galactocentric Cartesian Y coordinate, derived from dist50 |

zgal | double | pos.distance | kpc | StarHorse Galactocentric Cartesian Z coordinate, derived from dist50 |

rgal | double | pos.distance | kpc | StarHorse Galactocentric distance, derived from dist50 and assuming R_0 = 8.33 kpc |

ruwe | double | Gaia DR2 renormalised unit weight error (RUWE; Lindegren 2018) |